In a letter to Senate Majority Leader Bill Frist, R-Tenn., Labor Secretary Elaine Chao, Treasury Secretary John Snow and Commerce Secretary Donald Evans, said they would recommend Bush veto any legislation exacerbating the systemic underfunding of pension plans.
The Senate began debating the $25.5 billion corporate pension relief measure Thursday.
At issue are proposed provisions allowing commercial passenger airlines and steel manufacturers to reduce their required contributions significantly for two years.
The bill also provides the Treasury secretary the ability to lessen contribution requirements for companies having trouble meeting future contribution demands.
Critics contend the move endangers the budget of the federal agency that backs up private pensions, the Pension Benefit Guarantee Corp., which is already facing record deficits.
The measure also replaces the 30-year U.S. Treasury bond for calculating corporate pension plans payments with higher-rate corporate bonds for two years.
Business lobbyists in Washington, like the U.S. Chamber of Commerce, have argued that troubled businesses -- especially in the manufacturing arena --may be forced to freeze their pensions or even cancel them without the changes.